DBMB 711: Week 1 Innate Immune System Lecture

What are the five cardinal signs of inflammation?

Redness, heat, swelling, pain, and loss of function.

What is the main function of the immune system?

To recognize a threat (non-self antigen) and respond to it, while not reacting against the body's own cells (self-antigens).

What happens when the immune system is under-reactive?

It can lead to immunodeficiency, frequent infections, and cancers.

What are the three types of barriers in the innate immune system?

Anatomical (e.g., skin, mucous membranes), chemical (e.g., saliva, tears, mucus), and cellular (e.g., phagocytes).

The innate immune system uses ___ receptors (PRRs) to recognize threats.

pattern recognition

What do Pattern Recognition Receptors (PRRs) recognize on microbes?

They recognize patterns called PAMPs (Pathogen-Associated Molecular Patterns) or MAMPs (Microbe-Associated Molecular Patterns).

What are some examples of PAMPs?

Lipopolysaccharide (LPS) on gram-negative bacteria, peptidoglycan on gram-positive bacteria, viral double-stranded RNA, and glucans from fungal cell walls.

Why are Pattern Recognition Receptors (PRRs) described as "germline encoded"?

The genes for these receptors are part of our DNA, inherited from our parents, as a result of co-evolving with microbes over millions of years.

Where can Pattern Recognition Receptors (PRRs) be located on or in a cell?

They can be on the exterior surface of the cell (like Toll-like receptors), or in the interior (cytosol or nucleus).

What is the role of phagocytes in the immune response?

To capture and destroy bacteria and other antigens.

How do Natural Killer (NK) cells identify abnormal cells to kill?

NK cells look for the absence of MHC class I on a cell's surface. Virus-infected cells and tumor cells often down-regulate MHC class I, signaling the NK cell to kill them.

What is an antigen?

Any molecule (protein, lipid, etc.) that can elicit an immune response.

What are acute phase proteins, and where are they produced?

They are serum proteins, like C-reactive protein, produced by the liver in response to tissue-damaging infections and inflammation.

Why is C-reactive protein (CRP) clinically significant?

It is a key marker of systemic inflammation and is often checked in blood panels for patients with infections.

What is the complement system?

A group of over 30 proteins in body fluids that are part of the innate immune system and act as enzymes, regulators, and receptors.

What are the three main functions of the complement system?

1. Inflammation (via anaphylatoxins), 2. Lysis of target cells (via the Membrane Attack Complex), and 3. Opsonization (coating pathogens to enhance phagocytosis).

What is opsonization?

The process where a substance (an opsonin, like a complement protein or antibody) coats an antigen to make it more attractive for phagocytosis. The term comes from the Greek "to prepare for eating."

What is the Membrane Attack Complex (MAC)?

A complex of complement proteins that forms a pore in the membrane of a target cell (like a bacterium), leading to its lysis.

Where do all blood cells, including immune cells, originate from?

A hematopoietic stem cell in the bone marrow.

The hematopoietic stem cell gives rise to which two major progenitor cell lines?

The common myeloid progenitor and the common lymphoid progenitor.

Which immune cells primarily arise from the common myeloid progenitor and are associated with innate immunity?

Granulocytes (neutrophils, eosinophils, basophils), monocytes (which become macrophages), and dendritic cells.

Which immune cells primarily arise from the common lymphoid progenitor and are associated with adaptive immunity?

B cells and T cells (lymphocytes).

What is another name for neutrophils, and why are they called that?

PMNs (Polymorphonuclear cells), because of their multi-lobed, irregular-shaped nucleus.

What is the role of neutrophils?

They are the "first responders" in an infection, are highly phagocytic, and are the predominant white blood cell. Dead neutrophils are a major component of pus.

What are the functions of eosinophils and basophils?

They are primarily associated with allergic reactions and parasitic (worm) infestations.

What is the key characteristic of mast cells?

They are found only in tissues (not the bloodstream) and release granules containing histamine and leukotrienes, which cause allergy symptoms.

Monocytes circulate in the blood and differentiate into ___ when they move into tissues.

macrophages

Where do T cells mature?

They originate in the bone marrow and then travel to the thymus to complete their maturation.

Where do B cells mature?

They develop and mature entirely within the bone marrow.

What is the function of primary lymphoid organs?

They are the sites where immune cells develop and mature (e.g., bone marrow and thymus).

What is the function of secondary lymphoid organs?

They are the sites where the immune response is initiated, and where lymphocytes encounter antigens (e.g., lymph nodes, spleen, MALT).

What does MALT stand for, and what is its function in the oral cavity?

Mucosa-Associated Lymphoid Tissue; it is a secondary lymphoid tissue where immune responses are initiated against pathogens entering through mucosal surfaces.